Vehicle base structure

ABSTRACT

A vehicle base structure includes first and second structural members extending along a vehicle front-rear direction and disposed respectively at first and second sides of a vehicle base in a vehicle width direction, a battery unit disposed between the first and second structural members, and a bracket including a first wall portion fixed to a lower surface of one of the first and second structural members, a second wall portion extending inward in the vehicle width direction from an inner end portion of the first wall portion and inclined downward in a vehicle-height direction from the inner end portion of the first wall portion, and a third wall portion extending inward in the vehicle width direction from an inner end portion of the second wall portion inward in the vehicle width direction and being fixed to a lower surface of a battery case.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2020-036122 filed on Mar. 3, 2020, incorporated herein by reference inits entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a vehicle base structure.

2. Description of Related Art

There is disclosed technology in which a battery unit is installed in avehicle base (e.g., Japanese Unexamined Patent Application PublicationNo. 2009-57035 (JP 2009-57035 A)). In such technology, the battery unitis disposed using limited space between a pair of right and leftstructural members, for example.

SUMMARY

Now, in the above technology, in a broadside collision, inertia forceacts on the battery unit toward the collision side, and accordingly thebattery unit moves. However, the above related art has room forimprovement with regard to a point of lengthening the movement stroke(stroke over which movement is enabled) of the battery unit in abroadside collision, in the limited space of the vehicle base.

The disclosure provides a vehicle base structure in which the movementstroke of the battery unit in a broadside collision can be lengthened.

A vehicle base structure according to an aspect of the disclosureincludes first and second structural members extending along a vehiclefront-rear direction, the first and second structural members beingdisposed respectively at first and second sides of a vehicle base in avehicle width direction, a battery unit disposed between the first andsecond structural members, the battery unit including a battery case anda battery accommodated in the battery case, and a bracket including afirst wall portion fixed to a lower surface of one of the first andsecond structural members, a second wall portion extending inward in thevehicle width direction from an inner end portion of the first wallportion such that the second wall portion is inclined downward in avehicle-height direction from the inner end portion of the first wallportion, the inner end portion of the first wall portion being an endportion at an inward side of the first wall portion in the vehicle widthdirection, and a third wall portion extending inward in the vehiclewidth direction from an inner end portion of the second wall portion,the third wall portion being fixed to a lower surface of the batterycase, and the inner end portion of the second wall portion being an endportion at an inward side of the second wall portion in the vehiclewidth direction.

According to the above aspect, inertia force acts on the battery unittoward the collision side in a broadside collision. As the battery unitis displaced toward the structural member on the collision side, thebracket deforms with a connecting portion of the first wall portion andthe second wall portion and a connecting portion of the second wallportion and the third wall portion as starting points. At this time,inertia force toward the outward side in the vehicle width directionacts upon the connecting portion of the second wall portion and thethird wall portion, and moment centered on the connecting portion of thefirst wall portion and the second wall portion is generated. Now, thesecond wall portion extends inward in the vehicle width direction froman inner end portion of the first wall portion such that the second wallportion is inclined downward in a vehicle-height direction from theinner end portion of the first wall portion, and accordingly, when themoment is generated, a load acts on the battery unit, causing thebattery unit to be displaced from the installation position toward theoutward side in the vehicle width direction and the vehicle downwardside. Accordingly, the battery unit is guided from the installationposition toward the outward side in the vehicle width direction and thevehicle downward side. Thus, the movement stroke of the battery unit ina broadside collision is longer as compared to when the battery unitmoves horizontally toward the collision side in a broadside collision.

In the above aspect, the bracket may be fixed to the lower surface ofthe battery case, at an inner part of the third wall portion, the innerpart being at an inward side of the third wall portion in the vehiclewidth direction. The third wall portion may be configured to, when aload acts to move the battery unit from an installation position of thebattery unit outward in the vehicle width direction and downward in thevehicle-height direction, exhibit bending deformation under the load.

In the above aspect, a time when the load acts to move the battery unit,may be a time when a collision load is input to the first and secondstructural members from outward in the vehicle width direction andinertia force to outward in the vehicle width direction acts on aconnecting portion of the second wall portion and the third wall portionso that moment centered on a connecting portion of the first wallportion and the second wall portion is generated and the load acts tomove the battery unit.

According to the above configuration, when a collision load is input tothe structural member from the outward side in the vehicle widthdirection and inertia force to the outward side in the vehicle widthdirection acts on the connecting portion of the second wall portion andthe third wall portion of the bracket so that moment centered on theconnecting portion of the first wall portion and the second wall portionof the bracket is generated, the load acts to cause the battery unit tomove from the installation position thereof toward the outward side inthe vehicle width direction and also toward the vehicle downward side,and the third wall portion of the bracket exhibits bending deformationunder the load from the battery unit side. When the battery unit moveswhile causing bending deformation of the third wall portion of thebracket, a pivoting radius around the connecting portion of the firstwall portion and the second wall portion serving as the center ofpivoting can be made to be longer in comparison with when there is nobending deformation of the third wall portion (in other words, incomparison with when the length of the second wall portion as viewed inthe vehicle front-rear direction is the pivoting radius). As a result,the movement stroke of the battery unit can be made to be longer.

In the above aspect, the first and second structural members each mayhave a closed cross-section structure that extends along the vehiclefront-rear direction. The first and second structural members each mayinclude a first lower-wall portion that makes up a lower wall of acorresponding one of the structural members, the lower wall being at anoutward side of the corresponding one of the first and second structuralmembers in the vehicle width direction, a second lower-wall portiondisposed at a position that is inward of the first lower-wall portion inthe vehicle width direction and that is above the first lower-wallportion in the vehicle-height direction, the second lower-wall portionhaving a lower surface to which the first wall portion is fixed, and astepped portion that connects an inner end portion of the firstlower-wall portion and an outer end portion of the second lower-wallportion to each other along the vehicle-height direction, the inner endportion of the first lower-wall portion being at an inward side of thefirst lower-wall portion in the vehicle width direction, and the outerend portion of the second lower-wall portion being at an outward side ofthe second lower-wall portion in the vehicle width direction. Insideeach of the first and second structural members, a bulkhead may beprovided, the bulkhead being interposed between the stepped portion anda side-wall portion of a corresponding one of the first and secondstructural members, the side-wall portion being at the outward side ofthe corresponding one of the first and second structural members in thevehicle width direction.

According to the above configuration, the second lower-wall portion isset to a position that is inward of the first lower-wall portion in thevehicle width direction and that is above the first lower-wall portionin the vehicle-height direction of the first lower-wall portion, and thefirst wall portion of the bracket is fixed to the lower surface thereof.Accordingly, the first wall portion of the bracket can be set to aposition higher than the third wall portion, while securing length ofthe structural members in the vehicle up-down (vehicle-height)direction, and also maintaining the positions of the structural membersand of the battery unit in the vehicle up-down direction.

Also, with regard to the structural members, the end portion of thefirst lower-wall portion at the inward side in the vehicle widthdirection and the end portion of the second lower-wall portion at theoutward side in the vehicle width direction are connected along thevehicle up-down direction by the stepped portion, and the bulkhead isinterposed between the side-wall portion on the outer side in thevehicle width direction of structural members and the stepped portioninside the structural members. This bulkhead is capable of supportingthe second lower-wall portion when a load from the inward side in thevehicle width direction acts on the second lower-wall portion.Accordingly, when the inertia force toward the collision side acts onthe battery unit in a broadside collision and a load acts on the bracketfrom the inward side in the vehicle width direction, the structuralmembers and the bulkhead generate stable supporting reaction force.Thus, the battery unit can stably move while stably deforming thebracket.

In the above aspect, an under cover may be disposed below the batterycase in the vehicle-height direction. A protecting member may bedisposed adjacent to and outward of the battery case in the vehiclewidth direction, and be fastened along with the third wall portion ofthe bracket and the under cover.

According to the above configuration, the lower surface side of thebattery case is protected by the under cover, and the outward side inthe vehicle width direction of the battery case is protected by theprotecting member. Now, the protecting member is disposed adjacent tothe battery case at the outward side in the vehicle width direction, andis fastened along with the third wall portion of the bracket and theunder cover. Also, the third wall portion of the bracket is fixed to thelower surface of the battery case, as described above. Accordingly, evenwhen a load from the outward side in the vehicle width direction acts onthe protecting member when the battery unit moves due to the inertiaforce in a broadside collision and the bracket is deformed, the distancebetween the protecting member and the battery inside the battery casecan be suppressed from becoming shorter. As a result, the load can besuppressed from being input from the protecting member to the batteryvia the battery case in a broadside collision.

In the above aspect, the vehicle base structure may be a vehicle basestructure of a vehicle which includes a frame, in which a vehicle bodyhaving a cabin is supported on the frame. The first and secondstructural members may be side rails making up part of the frame.

According to the above configuration, the movement stroke of the batteryunit in a broadside collision, in which collision load is input to aside rail in a vehicle with a frame, can be lengthened.

In the above aspect, the third wall portion may include an exposedportion at which no member is disposed. A length of the exposed portionmay be set such that part of the battery case is allowed to bepositioned below the first wall portion and the second wall portion whenthe third wall portion exhibits bending deformation under the load.

In the above aspect, the bulkhead may be configured to, be capable ofsupporting the second lower-wall portion when a load is applied to thesecond lower-wall portion from inward in the vehicle width direction.

In the above aspect, the vehicle base structure may include a pluralityof the brackets, the plurality of the brackets including first andsecond brackets. The first wall portion of the first bracket may befixed to the lower surface of the first structural member. The firstwall portion of the second bracket may be fixed to the lower surface ofthe second structural member.

The above aspect of the disclosure yields excellent advantages in thatthe movement stroke of the battery unit in a broadside collision can belengthened.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like signs denote likeelements, and wherein:

FIG. 1 is a perspective view schematically illustrating a vehicle, inwhich a vehicle base structure according to an embodiment of thedisclosure is applied, in a state of collision with a pole;

FIG. 2 is a plan view illustrating a part of a vehicle base including aframe of the vehicle in FIG. 1;

FIG. 3 is an enlarged vertical sectional view in which a cross-sectiontaken along line III III in FIG. 2 is enlarged;

FIG. 4 is a perspective view illustrating a bulkhead in FIG. 3; and

FIG. 5 is a vertical sectional view illustrating the same cross-sectionin FIG. 3 in a broadside collision state.

DETAILED DESCRIPTION OF EMBODIMENTS

A vehicle base structure according to an embodiment of the disclosurewill be described with reference to FIGS. 1 through 5. Note that inthese drawings, an arrow FR that is shown where appropriate indicates avehicle forward side, an arrow UP indicates a vehicle upward side, anarrow W indicates a vehicle width direction, and an arrow IN indicatesan inward side in the vehicle width direction.

Configuration of Embodiment

FIG. 1 is a perspective view schematically illustrating a vehicle 10 towhich a vehicle base structure according to an embodiment is applied, ina state of collision with a pole. As one example, the vehicle 10according to the present embodiment is an electric vehicle that uses amotor, omitted from illustration, as a drive source. The vehicle 10 alsois a vehicle with a frame, and a vehicle body 14 that has a cabin 14C issupported upon a frame 12 (see FIG. 2).

FIG. 2 is a plan view illustrating part of a vehicle base 10A includingthe frame 12. The frame 12 is provided with side rails 20 as aright-left pair of structural members (first and second structuralmembers) extending along the vehicle front-rear direction, disposed atboth sides (first and second sides) of the vehicle base 10A in thevehicle width direction, respectively. The side rails 20 have a closedcross-section structure that extends along the vehicle front-reardirection (see FIG. 3).

The side rails 20 each have a middle rail portion 20C that makes up themiddle portion thereof in the vehicle front-rear direction and extendsalong the vehicle front-rear direction. Also, front-side rail portions20A that make up a front side of the side rails 20 and rear-side railportions 20B that make up a rear side of the side rails 20 extend alongthe vehicle front-rear direction, and are set to be situated at inwardof the middle rail portions 20C in the vehicle width direction and abovethe middle rail portions 20C in the vehicle up-down direction(vehicle-height direction). Front wheels, omitted from illustration, aredisposed at the outward side in the vehicle width direction of thefront-side rail portions 20A of the side rails 20, and rear wheels,omitted from illustration, are disposed on the outward side in thevehicle width direction of the rear-side rail portions 20B of the siderails 20. Also, the front-side rail portions 20A and middle railportions 20C of the side rails 20 are linked by front-side linking railportions 20D, and the rear-side rail portions 20B and the middle railportions 20C of the side rails 20 are linked by rear-side linking railportions 20E.

The side rails 20 have the front-side portions thereof linked to eachother by a plurality of crossmembers 22A, 22B, and 22C extending alongthe vehicle width direction. The side rails 20 also have the rear-sideportions thereof linked to each other by a plurality of crossmembers22D, 22E, and 22F extending along the vehicle width direction. Thesecrossmembers 22A, 22B, 22C, 22D, 22E, and 22F make up part of the frame12.

A plurality of pairs of front-side mount portions M1, M2, and M3, forsupporting the front-side portion of the vehicle body 14 (see FIG. 1),is provided at the front-side portions of the side rails 20. Also, aplurality of pairs of rear-side mount portions M4, M5, and M6, forsupporting the rear-side portion of the vehicle body 14 (see FIG. 1), isprovided at the rear-side portions of the side rails 20.

FIG. 3 is an enlarged vertical sectional view in which a cross-sectiontaken along line in FIG. 2 is enlarged. The middle rail portion 20C ofthe side rail 20 is composed of an inner panel 24 and an outer panel 26that are joined, as illustrated in FIG. 3.

The outer panel 26 makes up a portion of the middle rail portion 20Cthat is at the outward side in the vehicle width direction, and has anopen cross-sectional form that is opened toward the inward side in thevehicle width direction, when a vertical section thereof is viewed inthe vehicle front-rear direction. More specifically, the outer panel 26is provided with an outer upper-wall portion 26A, an outer side-wallportion 26B that is bent from the end portion of the outer upper-wallportion 26A at the outward side in the vehicle width direction andextends toward the vehicle downward side, and an outer lower wallportion 26C that is bent and extends toward the inward side in thevehicle width direction from the lower end portion of the outerside-wall portion 26B.

The inner panel 24 makes up a portion of the middle rail portion 20Cthat is at the inward side in the vehicle width direction, and has anopen cross-sectional form that is opened toward the outward side in thevehicle width direction, when a vertical section thereof is viewed inthe vehicle front-rear direction. The inner panel 24 is configured toinclude an inner upper-wall portion 24A that is joined to the outerupper-wall portion 26A, and an inner first lower-wall portion 24E thatis joined to the outer lower wall portion 26C.

A portion of the inner upper-wall portion 24A at the outward side in thevehicle width direction overlaps from below and is joined to a portionof the outer upper-wall portion 26A at the inward side in the vehiclewidth direction. The inner first lower-wall portion 24E overlaps fromabove and is joined to a portion of the outer lower wall portion 26C atthe inward side in the vehicle width direction. Also, the end portion ofthe inner first lower-wall portion 24E at the inward side in the vehiclewidth direction generally matches the end portion of the outer lowerwall portion 26C at the inward side in the vehicle width direction.Further, the end portion of the inner first lower-wall portion 24E atthe inward side in the vehicle width direction is set to be situated ata position further to the outward side in the vehicle width directionthan the end portion of the inner upper-wall portion 24A at the inwardside in the vehicle width direction.

Also, the inner panel 24 is provided with an inner side-wall portion 24Bthat is bent toward the vehicle downward side from the end portion ofthe inner upper-wall portion 24A at the inward side in the vehicle widthdirection and extends downward, and a bent wall portion 24X thatconnects the lower end portion of the inner side-wall portion 24B andthe end portion of the inner first lower-wall portion 24E at the inwardside in the vehicle width direction. The position of the lower end ofthe inner side-wall portion 24B in the vehicle up-down direction is setto be a position that is higher than the position of the lower end ofthe outer side-wall portion 26B in the vehicle up-down direction. Thebent wall portion 24X is provided with an inner second lower-wallportion 24C that is bent to extend to the outward side in the vehiclewidth direction from the lower end portion of the inner side-wallportion 24B and serves as a second lower-wall portion, and also isprovided with a stepped portion 24D that connects the end portion of theinner first lower-wall portion 24E at the inward side in the vehiclewidth direction and the end portion of the inner second lower-wallportion 24C at the outward side in the vehicle width direction, alongthe vehicle up-down direction. The stepped portion 24D is somewhatinclined to the inward side in the vehicle width direction, toward thevehicle upward side.

A portion made up of the outer lower wall portion 26C and the innerfirst lower-wall portion 24E makes up a lower wall at the outward sidein the vehicle width direction of the middle rail portion 20C, and willbe referred to as a first lower-wall portion 25 in the followingdescription. The above-described inner second lower-wall portion 24C isset to a position that is inward of the first lower-wall portion 25 inthe vehicle width direction and that is above first lower-wall portion25 in the vehicle up-down direction.

A bulkhead 28 that is interposed between the outer side-wall portion 26Bthat is the side wall portion of the middle rail portion 20C at theoutward side in the vehicle width direction and the stepped portion 24D,is provided inside of the middle rail portion 20C of the side rail 20.The bulkhead 28 is made of a metal plate, for example. FIG. 4illustrates the bulkhead 28 in a perspective view. Note that in FIG. 4,part of the middle rail portion 20C in a state with the bulkhead 28provided thereto is indicated by imaginary lines (long dasheddouble-short dashed lines).

As illustrated in FIG. 4, the bulkhead 28 extends along the vehiclewidth direction, and the cross-sectional shape thereof orthogonal to thevehicle width direction is a general hat shape that opens downwards inthe vehicle up-down direction. A pair of flange portions 28F that makeup the lower end portion of the bulkhead 28 and that are arrayed in thevehicle front-rear direction are overlaid on the first lower-wallportion 25 and joined thereto by welding. In the present embodiment, thebulkhead 28 is provided at a middle portion in the vehicle front-reardirection inside the middle rail portion 20C as one example. Note that aplurality of bulkheads 28 may be provided within the middle rail portion20C and arrayed in the vehicle front-rear direction. In this case, thebulkheads 28 preferably are provided at a plurality of parts includingthe middle portion in the vehicle front-rear direction inside the middlerail portion 20C.

An upper surface of an upper wall portion 28A of the bulkhead 28 isflush with an upper surface of the inner second lower-wall portion 24Cof the middle rail portion 20C, as illustrated in FIG. 3. Also, the endface of the bulkhead 28 at the outward side in the vehicle widthdirection is disposed adjacent with (more specifically, in planarcontact with) the outer side-wall portion 26B at the outward side in thevehicle width direction of the middle rail portion 20C. Further, the endface of the bulkhead 28 at the inward side in the vehicle widthdirection is somewhat inclined to the inward side in the vehicle widthdirection, toward the vehicle upward side, and is disposed adjacent with(more specifically, in planar contact with) the stepped portion 24D ofthe middle rail portion 20C. According to the above, the bulkhead 28 iscapable of supporting the inner second lower-wall portion 24C when aload is applied to the inner second lower-wall portion 24C from theinward side in the vehicle width direction.

As illustrated in FIG. 2, a battery unit 30 (illustrated in a simplifiedform in FIG. 2) is disposed between the side rails 20. Note that a frontportion of the battery unit 30 is attached to the crossmember 22C usingan attachment member (omitted from illustration), and a rear portion ofthe battery unit 30 is attached to the crossmember 22D using anattachment member (omitted from illustration), although detailedillustration thereof is omitted.

As illustrated in FIG. 3, the battery unit 30 is a unit in which abattery 32 (illustrated in a simplified form in FIG. 3) is accommodatedin a battery case 34. The battery 32 is for supplying electric power toa motor (omitted from illustration) that is the drive source of thevehicle 10 (see FIG. 1), and is also referred to as a fuel cell stack.The battery case 34 is made of a lower case 36 and an upper case 38 thatare joined. A flange portion 36F extends outwards from an opening edgeof the lower case 36 that is opened toward the upward side. Conversely,a flange portion 38F extends outwards from an opening edge of the uppercase 38 that is opened toward the downward side. The upper case 38 islaid on the lower case 36 so as to be overlaid in planar view of thevehicle, and the flange portion 38F of the upper case 38 is overlaid onthe flange portion 36F of the lower case 36 and joined. This batterycase 34 is not joined to a floor panel 14F of the cabin 14C (see FIG. 1for either).

Reinforcements 39, which are L-shaped as viewed in the vehiclefront-rear direction, are disposed at corner portions of the lower case36 on both sides in the vehicle width direction. Erect wall portions 39Aof the reinforcements 39 are joined to erect wall portions 36A of thelower case 36 by spot welding or the like. Lower wall portions 39B ofthe reinforcements 39 are also joined to lower wall portions 36B of thelower case 36 by spot welding or the like. The length of the lower wallportions 39B as viewed in the vehicle front-rear direction is set to belonger than the length of the erect wall portions 39A.

The middle rail portions 20C and the battery unit 30 are linked bybrackets 40. The brackets 40 are, in one example, metal members composedof slender plate members. The brackets 40 extend along the vehiclefront-rear direction, as illustrated in a simplified form in FIG. 2. Thelength of the brackets 40 in the vehicle front-rear direction is set togenerally correspond to the length of the battery unit 30 in the vehiclefront-rear direction. The bracket 40 has a first wall portion 42 that isfixed to the lower surface of the inner second lower-wall portion 24C ofthe middle rail portion 20C by a bolt 54 and a nut 55, as illustrated inFIG. 3. The end position of the first wall portion 42 of the bracket 40at the outward side in the vehicle width direction generally matches theend position of the inner second lower-wall portion 24C of the middlerail portion 20C at the outward side in the vehicle width direction.Also, the end position of the first wall portion 42 of the bracket 40 atthe inward side in the vehicle width direction generally matches the endposition of the inner second lower-wall portion 24C of the middle railportion 20C at the inward side in the vehicle width direction.

The bracket 40 also is provided with a second wall portion 44 thatextends inward in the vehicle width direction from an inner end portionof the first wall portion 42 such that the second wall portion 44 isinclined downward in a vehicle-height direction from the inner endportion of the first wall portion 42, and further is provided with athird wall portion 46 extending inward in the vehicle width directionfrom an inner end portion of the second wall portion 44 that is an endportion at an inward side of the second wall portion 44 in the vehiclewidth direction. The third wall portion 46 is fixed to the lower surfaceof the battery case 34 at that part at the inward side in the vehiclewidth direction, by spot welding or the like.

On the other hand, a protecting member 50 is disposed adjacent to (morespecifically, in planar contact with) an outer peripheral side of thebattery case 34 including the outward side in the vehicle widthdirection. The protecting member 50 is made of metal in one example, andis disposed along the perimeter of the battery case 34 at the downwardside of the flange portions 36F and 38F of the battery case 34. Theprotecting member 50 has a rectangular closed cross-sectional structurethat extends along the perimeter of the battery case 34, and is disposedon top of a middle portion of the third wall portion 46 of the bracket40 in the vehicle width direction.

Also, an under cover 52 is disposed at the downward side of the batterycase 34. The under cover 52 covers the battery case 34 from the downwardside of the vehicle, and the perimeter portion of the under cover 52 ispositioned at the downward side of the protecting member 50. The undercover 52 is laid on part of the third wall portion 46 of the bracket 40from the lower surface side. A lower wall portion 50A of theabove-described protecting member 50 is fastened by a bolt 56 and a nut57 along with the third wall portion 46 of the bracket 40 and the undercover 52. The under cover 52 is made of metal in one example.

According to the above, the third wall portion 46 of the bracket 40 isprovided with an exposed portion 46A at which no other members,including the battery unit 30, are disposed, over a predetermined rangein the vehicle width direction from the end portion thereof at theoutward side in the vehicle width direction. The bracket 40 isconfigured such that when a collision load C is input to the middle railportion 20C from the outward side in the vehicle width direction andinertia force f1 to the outward side in the vehicle width direction actson a connecting portion (in other words, a boundary portion) 45 of thesecond wall portion 44 and the third wall portion 46, moment M centeredon a connecting portion (in other words, a boundary portion) 43 of thefirst wall portion 42 and the second wall portion 44 is generated, and aload f2 acts to cause the battery unit 30 to move from the installationposition thereof toward the outward side in the vehicle width directionand also toward the vehicle downward side. The third wall portion 46 isconfigured to exhibit bending deformation at the end portion of theexposed portion 46A at the inward side in the vehicle width direction,under the load (see arrow f2) from the battery unit 30 side when thisload f2 acts thereupon (see FIG. 5). The length of the exposed portion46A in the vehicle width direction is set to be such a length that adeformation mode, in which the bracket 40 is deformed and the tip sidesof the flange portions 36F and 38F of the battery case 34 come to besituated at the downward side of the first wall portion 42 and thesecond wall portion 44 in a broadside collision, as illustrated in FIG.5, can be realized.

Effects and Advantages of Embodiment

Next, the effects and advantages of the present embodiment will bedescribed.

In the present embodiment, when a pole P that is a colliding objectcollides with the middle rail portion 20C of the side rail 20 from theoutward side in the vehicle width direction in a broadside collision, asillustrated in FIG. 3, inertia force F acts on the battery unit 30toward the collision side. As the battery unit 30 is displaced towardthe middle rail portion 20C on the collision side, the bracket 40deforms with the connecting portion 43 of the first wall portion 42 andthe second wall portion 44 and the connecting portion 45 of the secondwall portion 44 and the third wall portion 46 as starting points.

At this time, inertia force f1 toward the outward side in the vehiclewidth direction acts upon the connecting portion 45 of the second wallportion 44 and the third wall portion 46, and moment M centered on theconnecting portion 43 of the first wall portion 42 and the second wallportion 44 is generated. Now, the second wall portion 44 is inclinedfrom the end portion at the inward side in the vehicle width directionof the first wall portion 42 to the inward side in the vehicle widthdirection, toward the vehicle downward side, and accordingly, when themoment M is generated, the load f2 acts on the battery unit 30, causingthe battery unit 30 to be displaced from the installation positiontoward the outward side in the vehicle width direction and the vehicledownward side. Accordingly, the battery unit 30 is guided from theinstallation position toward the outward side in the vehicle widthdirection and the vehicle downward side. Thus, the movement stroke ofthe battery unit 30 in a broadside collision is longer as compared towhen the battery unit moves horizontally toward the collision side in abroadside collision.

Also, in the present embodiment, when the load f2 that causes thebattery unit 30 to move from the installation position toward theoutward side in the vehicle width direction and the vehicle downwardside acts on the battery unit 30, the third wall portion 46 of thebracket 40 exhibits bending deformation at the end of the exposedportion 46A at the inward side in the vehicle width direction under theload (see arrow f2) from the battery unit 30 side (see FIG. 5). When thebattery unit 30 moves to the position of the battery unit 30 illustratedin FIG. 5, for example, as the third wall portion 46 of the bracket 40exhibits bending deformation, a pivoting radius around the connectingportion 43 of the first wall portion 42 and the second wall portion 44serving as the center of pivoting can be made to be longer as comparedwith when there is no bending deformation of the third wall portion 46(in other words, in comparison with when the length of the second wallportion 44 as viewed in the vehicle front-rear direction is the pivotingradius). As a result, the movement stroke of the battery unit 30 can bemade to be longer. Note that bending deformation of the third wallportion 46 can also increase the amount of energy absorbed.

Also, in the present embodiment, the inner second lower-wall portion 24Cof the middle rail portion 20C is set to a position on the inward sidein the vehicle width direction and on the upward side in the vehicleup-down direction from the first lower-wall portion 25, and the firstwall portion 42 of the bracket 40 is fixed to the lower surface thereof,as illustrated in FIG. 3. Accordingly, the first wall portion 42 of thebracket 40 can be set to a position higher than the third wall portion46, while securing length of the middle rail portion 20C in the vehicleup-down direction and also maintaining the positions of the middle railportion 20C and of the battery unit 30 in the vehicle up-down direction.

Also, in the present embodiment, with regard to the middle rail portion20C, the first lower-wall portion 25 and the inner second lower-wallportion 24C are connected by the stepped portion 24D, and the bulkhead28 is interposed between the outer side-wall portion 26B of the middlerail portion 20C and the stepped portion 24D inside the middle railportion 20C. The bulkhead 28 is capable of supporting the inner secondlower-wall portion 24C when a load from the inward side in the vehiclewidth direction acts on the inner second lower-wall portion 24C.Accordingly, when the inertia force F toward the collision side acts onthe battery unit 30 in a broadside collision and a load acts on thebracket 40 from the inward side in the vehicle width direction, themiddle rail portion 20C and the bulkhead 28 generate stable supportingreaction force. Thus, the battery unit 30 can stably move while stablydeforming the bracket 40 (see FIG. 5).

As described above, according to the vehicle base structure of thepresent embodiment, the movement stroke of the battery unit 30 in abroadside collision can be lengthened.

Also, in the present embodiment, the lower surface side of the batterycase 34 is protected by the under cover 52, and the outward side in thevehicle width direction of the battery case 34 is protected by theprotecting member 50. Now, the protecting member 50 is disposed adjacentto the battery case 34 at the outward side in the vehicle widthdirection, and is fastened along with the third wall portion 46 of thebracket 40 and the under cover 52. Also, the third wall portion 46 ofthe bracket 40 is fixed to the lower surface of the battery case 34, asdescribed above. Accordingly, even when a load from the outward side inthe vehicle width direction acts on the protecting member 50 illustratedin FIG. 5 and the battery unit 30 moves due to the inertia force F in abroadside collision and the bracket 40 is deformed, the distance betweenthe protecting member 50 and the battery 32 inside the battery case 34can be suppressed from becoming shorter. As a result, a load can besuppressed from being input from the protecting member 50 to the battery32 via the battery case 34 (more specifically, the erect wall portion36A of the lower case 36) in a broadside collision.

Supplementary Description of Embodiment

Note that in the present embodiment, the first lower-wall portion 25,the inner second lower-wall portion 24C, and the stepped portion 24D areprovide on the middle rail portion 20C, as illustrated in FIG. 3 andother drawings. However, a configuration may be made in which the lowerwall portion of the structural member is not stepped, but instead has aflat shape. For example, a middle rail portion (portion constituting themiddle portion of the structural member in the vehicle front-reardirection) provided with a lower-wall portion set to a position of theinner second lower-wall portion 24C in the vehicle up-down direction,illustrated in FIG. 3, may be applied instead of the middle rail portion20C of the above embodiment. In this case, a reinforcing member forreinforcing the lower-wall portions may be provided.

Also, in the present embodiment, the bracket 40 is fixed to the lowersurface of the battery case 34 at a part of the third wall portion 46 atthe inward side in the vehicle width direction, which is a preferableconfiguration, but a configuration may be made in which the bracket 40is fixed to the lower surface of the battery case 34 at a part includinga part of the third wall portion 46 at the outward side in the vehiclewidth direction.

Also, in the present embodiment, the protecting member 50 is fastenedalong with the third wall portion 46 of the bracket 40 and the undercover 52, but a configuration may be made in which the protecting memberis fastened by bolting to the third wall portion 46 of the bracket 40alone. Further, a configuration may be made in which the protectingmember 50 is not provided.

Also, in the present embodiment, the vehicle 10 is described as avehicle with a frame, but the vehicle base structure according to thedisclosure may be applied to a vehicle with a frameless structure(monocoque structure). Also, in the present embodiment, the structuralmembers are the side rails 20, but the structural members may be rockerpanels (also referred to as side sills) of a frameless-structurevehicle.

Note that the above embodiment and the above modifications may becombined and carried out as appropriate.

Although an example of the disclosure has been described above, thedisclosure is not limited to the above, and it is needless to say thatthe disclosure may be carried out by arrangements other than the above,modified variously, without departing from the scope thereof.

What is claimed is:
 1. A vehicle base structure comprising: first andsecond structural members extending along a vehicle front-reardirection, the first and second structural members being disposedrespectively at first and second sides of a vehicle base in a vehiclewidth direction; a battery unit disposed between the first and secondstructural members, the battery unit including a battery case and abattery accommodated in the battery case; and a bracket including afirst wall portion fixed to a lower surface of one of the first andsecond structural members, a second wall portion extending inward in thevehicle width direction from an inner end portion of the first wallportion such that the second wall portion is inclined downward in avehicle-height direction from the inner end portion of the first wallportion, the inner end portion of the first wall portion being an endportion at an inward side of the first wall portion in the vehicle widthdirection, and a third wall portion extending inward in the vehiclewidth direction from an inner end portion of the second wall portion,the third wall portion being fixed to a lower surface of the batterycase, and the inner end portion of the second wall portion being an endportion at an inward side of the second wall portion in the vehiclewidth direction.
 2. The vehicle base structure according to claim 1,wherein: the bracket is fixed to the lower surface of the battery case,at an inner part of the third wall portion, the inner part being at aninward side of the third wall portion in the vehicle width direction;and the third wall portion is configured to, when a load acts to movethe battery unit from an installation position of the battery unitoutward in the vehicle width direction and downward in thevehicle-height direction, exhibit bending deformation under the load. 3.The vehicle base structure according to claim 1, wherein: the first andsecond structural members each have a closed cross-section structurethat extends along the vehicle front-rear direction; the first andsecond structural members each include a first lower-wall portion thatmakes up a lower wall of a corresponding one of the first and secondstructural members, the lower wall being at an outward side of thecorresponding one of the first and second structural members in thevehicle width direction, a second lower-wall portion disposed at aposition that is inward of the first lower-wall portion in the vehiclewidth direction and that is above the first lower-wall portion in thevehicle-height direction, the second lower-wall portion having a lowersurface to which the first wall portion is fixed, and a stepped portionthat connects an inner end portion of the first lower-wall portion andan outer end portion of the second lower-wall portion to each otheralong the vehicle-height direction, the inner end portion of the firstlower-wall portion being at an inward side of the first lower-wallportion in the vehicle width direction, and the outer end portion of thesecond lower-wall portion being at an outward side of the secondlower-wall portion in the vehicle width direction; and inside each ofthe first and second structural members, a bulkhead is provided, thebulkhead being interposed between the stepped portion and a side-wallportion of a corresponding one of the first and second structuralmembers, the side-wall portion being at the outward side of thecorresponding one of the first and second structural members in thevehicle width direction.
 4. The vehicle base structure according toclaim 1, wherein: an under cover is disposed below the battery case inthe vehicle-height direction; and a protecting member is disposedadjacent to and outward of the battery case in the vehicle widthdirection, and is fastened along with the third wall portion of thebracket and the under cover.
 5. The vehicle base structure according toclaim 1, wherein: the vehicle base structure is a vehicle base structureof a vehicle which includes a frame and in which a vehicle body having acabin is supported on the frame; and the first and second structuralmembers are side rails making up part of the frame.
 6. The vehicle basestructure according to claim 2, wherein: the third wall portion includesan exposed portion at which no member is disposed, and a length of theexposed portion is set such that part of the battery case is allowed tobe positioned below the first wall portion and the second wall portionwhen the third wall portion exhibits bending deformation under the load.7. The vehicle base structure according to claim 2, wherein a time whenthe load acts to move the battery unit, is a time when a collision loadis input to the first and second structural members from outward in thevehicle width direction and inertia force to outward in the vehiclewidth direction acts on a connecting portion of the second wall portionand the third wall portion so that moment centered on a connectingportion of the first wall portion and the second wall portion isgenerated and the load acts to move the battery unit.
 8. The vehiclebase structure according to claim 3, wherein the bulkhead is configuredto, be capable of supporting the second lower-wall portion when a loadis applied to the second lower-wall portion from inward in the vehiclewidth direction.
 9. The vehicle base structure according to claim 1,wherein the vehicle base structure includes a plurality of the brackets,the plurality of the brackets including first and second brackets, thefirst wall portion of the first bracket is fixed to the lower surface ofthe first structural member, and the first wall portion of the secondbracket is fixed to the lower surface of the second structural member.